Continuous inductive train-control system



Feb. 21, 1928. 1,660,133

} E. H. LOFTlN CQNTINUOUS INDUCTIVE TRAIN CONTROL SYSTEM Filed Dec. 1925 Patented Feb. 21, 1928.

EDWARD H. LOFTIN, or NEW YORK, Nz'Y AssIGNo-R-ro GENERAL RAILWAY'SIGNAL COMPANY, or ROCHESTER, NEW YORK.

oon'rmuous ZENDUGTIVE TRAIN-CONTRODSYSTEM.

Application filed, December This invention relates to automatic train control and more particularly.concerns means for amplifying impulses received from the trackway in a train. control system of the continuous inductive type.

In train control systems of the well known continuously inductive type, influences, corresponding to traffic conditions are continuously transmitted from the trackway toya moving vehicle, the transmissionof such influences being usually accomplished by electro-magnetic induction. As the. air-gap through which the electro-magnetic induction must act is necessarily large, and the voltages induced in the car-carried receiving means necessarily small, it is essential to the satisfactory operation of any practical and reliable car-carried control.equipment that some form of amplifying means be employed. Such amplifying means must be extremely sensitive, responding to-relatively small volt.- ages, must use very little energy in its input circuit, and must be capable of delivering a suitable amount of energy from its output circuit to operate the car-carried control devices.

lVith the above andother considerations in mind it is proposed in; accordance with the present invention to provide a novel type of amplifying means for continuous inductive train control systems ,'and, more specifically it is proposed to provide amplifying means employing the principle of the electro-statie brake for responding to thefreceived impulses and controlling car, circuits carrying appreciable currents in accordance with the reception of such impulses;

Other objects, advantages and characteristic features of the invention will become apparent as the description thereof progresses. v v r r V In. describing.tlieinven-tion in detail, reference will be made to the accompanying drawingin Which:

Figure 1 represents. in a diagrammatic and simplified manner atypical train control system of the contmuons inductivetype embodying theamplifying means of the presentinvention;

F'gure 2, represents, amodified form of amplifying means applied to the car apparas tus of a'continuous inductive train control system; and

Figure 3 represents a second modification 5, 1925. se riaino. 73,407;

ofthetrain control amplifying means shown in Figure l. f i f Referring first to Figure 1, an extremely simple two-position type. of continuous -in ductive train control system hasbeen chosen for the purpose of illustrating the invention, it being understood that the'invention is equally applicable to any other type of continuous inductive traincontrol. system.

,The trackway apparatus isof the. type well known in the art, and requires'but little explanation to those familiar with railway signalling and train control practice. The track rails lare divided intoblocks by the insulating joints 2, the block land the ad j-a centends of theblocksH and J having, been shown. The corresponding devices in the several blocks are represented by like'referonce characters having distinctive exponents. Suitable .track relays 3 are, connected across the track rails at the entrance ends of: the blocks. as shown, being normally energized by current from the, track batteries. 4, connected across the track rails at the exit end of each block.' Alternating. train control current of a suitable frequency is applied to the two track rails 1 in series by a transformer 5 connectingin series with the track battery '4: at the exit end of each block, the.

primary Winding of this transformer being energized from. the transmission line 6 through the contacts 7 and 8 of. the track relay 3 of the first block in advance..- It is evident that the; presence of a trainin a given block, say the block J, shunts the track circuit and train control current from the, track rails l behind the train in that block, causing'the de-energizationyof the track relay ti at the entrance end of. the

block. The de-energization of this. track relay 3 causes the traincontrol current to be cut off from the first'block I; in the rear of the occupied. block; by breaking the energize ing circuit for thetra-nsformer 5 through the contacts 7 and 8 Wayside signals ofthe color-light, semaphore or other suitabletype may o-rzmaynot be used inconnection with the'trackw-ayapparatus of the system, and for the purpose of illustration, the semaphore-signals Z have been conventionally shown at the entrance end. of each block, their Well known operatingdevices andc-ircuits having been omitted to simplify the disclosure.

A railway vehicle has been conventionally illustrated in the block H by the wheels and axles 9. This vehicle is provided with suitable receiving apparatus which in the present embodiment comprises the receiving coils 10. These coils, which may or may not be provided with laminated iron cores, are connected in such amanner that voltages induced therein by alternating currents fiwing in opposite directions in the track rails are additive.

The circuit through the coils is connected as shown to the winding 11 of an electro-mechanical relay R which may take any suitable form, but preferably comprises a laminated U-shaped core structure 12 having a winding 11 thereon and provided with an armature 13 having a reed or contact element 1 1 soldered or otherwise suitably secured thereto. The armature 13 and the reed 1 1 are preferably mechanically tuned to resonate at the frequency of the train control alternating current. The circuit through the winding 11 of the relay R is preferably tuned to resonate at the frequency employed by means of a condenser 15.

The amplifying apparatus includes a device generally known as an electrostatic brake. It has been found by experiment that if an electrical semi-conductor such as agate, marble, flint, slate, or lithographic stone, having a smooth surface, is inserted between two good electrical conductors such 'as metallic plates so as to have good surface contact therewith, and if an electrical difference of potential is applied between the metallic plates, there results a strong attraction or adhesion between the semi-conductor and the plates. The adhesion does not occur until good surface contact has been established between both of the conductors and the semi-conductor, and hence can only be utilized to advantage by the use of special apparatus.

One theory which has been advanced in explanation of this phenomenon is as follows. The surface resistance between the conducting plates and the semi-conductor is large in proportion to the internal resistance of the semi-conductor, and for this rea.

son a high electrical tension exists at the point of contact between the plate and the semi-conductor. This high electrical tension or difference in electro-static charge causes the adhesion or attraction between the bodies. I

In the embodiment of the invention shown in Fig. 1, the electrostatic brake apparatus takes the form of a cylinder 16 of suitable semi-conducting material such as agate, carried on a rotating shaft 17 of low resistance conducting material such as copper or brass. A brake band or strap 18 of thin flexible conducting material such as phosphor-bronze, is

held in intimate contact with the surface of the agate cylinder 16 by the spring 19, the surfaces of the cylinder and of the band being carefully polished to insure as great an area of intimate surface contact as possible. The brake band 18 is connected at one end to the tensioned spring 19 and at the other end to the diaphragm 20 of a suitable sensitive electrical translating device, which in the present embodiment takes the form of a microphone or transmitter T. This transmitter comprises a case 21 of insulating material having'a conducting plate 22 supported therein and being filled with a suitable variable resistance substance such as granulated carbon, the arrangement being such that a small variation in the pressure on the conducting diaphragm'QO causes a variation in the resistance of the circuit between the diaphragm 20 and the plate 22. The shaft 17 of the electrostatic brake is continuously rotated by a suitable means such as the electric motor E. It is evident that variations in adhesion between the, band 18 and the cylinder 16 caused by variations in potential between the band 18 and the shaft 17 will cause the band to alternately grip and release the cylinder, thus causing vibrations to be transmitted to the microphone or transmitter ,T which in turn causes variations in the current flow therethrough. It should be noted that the power band 18 and the cylinder 16 merely serving to control the application of this power. For this reason the device consumes very little energy.

The transmitter T' is connected through a filter circuitto a circuit including a rectifier 23 and a suitable sensitive relay 24 of the direct current type. The rectifier 23 may take any suitable form, and as shown comprises the well known crystal detector. The rectifier may of course be omitted and a suit ably sensitive alternating current relay may be used in place of the direct current relay shown.

As the particular train speed or brake control apparatus used forms no part of the present invention, no particular or specific apparatus of this type has been shown. As the initiation of an automatic brake application, a restrictive speed control'or the display of an unfavorable cab signal indication is usually accomplished by the de-energization of some suitable electro-magnetic device,

the device TC has been shown, it being as- I sumed that the de-energization of this device acts in some suitable manner to restrict the progress of the train or to inform the engineer that unfavorable traffic conditions exist.

Operation; Fig. I,

The various devices have been shown in their normal. operatingpositions, that is, the

positions assumed when the equipped vehicle istravelling under clear tra-fiic conditions with al-lsci-rcu-its and devices. properly ener gizedt, For convenience, the letters B and- C have. been used to designate the opposite poles of a. suitable source of energy, preferably astorage battery.

Considering first. the operation of the sys-. tem of Fig. l -under cleartraflic conditions, assume that an equipped train is travelling in. aclear block, that. is,,withv no other train in the block in which. the; trainunder con; sideration is located or in the first block: in

.. advance thereof. Under these conditions,

alternating current flows in thetrack rails in advance of the train,.and serves to induce alternating voltages in-the receivingcoils 10. These voltages are impressed on. the winding 11 of.- the relay B through the 'tuned'receiving circuit including the condenser 15, and

as the moving elements of; the relay R are mechanically tuned. to resonance at the train control frequency, the reed or contact element together with the armature 13 is caused to vibrate, the energy consumption inv the. receiving circuit being very lowby reason of the electrical and mechanical T tuning. This vibration of the contact element '14 causes its intermittentcontact: with the adjustable stationary con-tactz25, andthus impresses an intermittent or pulsating voltage between the metallic shaft'l? and the. band- 18 of the electrostatic brake through a par tial circuit which may be traced asfollows from the positive. terminal of theibattery' 26, wire 27, stationary contact 25, contact element 14, armature 13, wire 28,"band -18, shaft 17, wire 29 to the negative terminal of battery 26, As explained above, an. adhesion occurs between the band 18 andv the cylinder 16 causing theband to'grip and slip on-the cylinder and thus transmitting vibrations to the diaphragm 20 of the transmitter T. The vibration of the diapl1rag1n20 causes variations in resistance in the circuit through the transmitter, and a pulsatingicurrent flows through-the transmitter T, the battery 30 and the primary winding of the trans-. former 31, the circuit being obvious from the drawings. The secondary winding 'of the transformer 31 is connected through a condenser 32-to-the primary winding of. a second transformer 33 through a circuit whichxis obvious from the drawing. This circuit. be tween the transformers 31 and 33=is tuned to resonate at the train control frequency, and acts to filter or choke out undersirable frequencies caused by stray currents in'the. track rails or'in power lines adjacent thereto, .or by variations in the frictionbetween the band 18 and a cylinder 16. The alternating current from the transformers33 is rectified by the rectifier 23' and energizes the 'relay24, causing its contact finger 34 to engage its fronticontact. With the relay 24 thus energized, thetrain control device TC is energizedthroughacircuit which is obvious from the drawings. The energization of the device TC prevents the automatic appl-ication of the brakes or other automatic restriction, and the train under consideration proceeds through the clear block under the control of'the engineer. 7

When the-train under consideration enters a. block in which caution traffic conditions exist,- that is, the firstblock in the rear of an occupied block, no train control current flows in. the track rails and the relay R does not vibrate. is applied between the shaft 17 and the band 18' ofthe electrostatic brake, and the inichrophone or transmitter T is not actuated, hence the relay 24: and the device TC are deenergized. The de-energization of the train control device T'C causes an automatic brake application, a speed restriction. or other restrictive control.

As the train under consideration proceeds in .an occupied or danger block, the train control current is stillcut oil from the track rail-s, and the car-carried apparatus remains in the condition-described above in connecion with the-operation in a caution block. The restrictive control-persists, maintaining thetrain-at a safe speed or bringing it to a stop as desired.

' In Fig.2 a modified form of car-carried apparatus has been illustrated. In this modification, a tuned relay 36, identical with Under these conditions no voltage the relay R shown in Fig. 1, is employed to vary the potential applied to an electro-static brake. The band 37 [of this brake is held in intimate contact withthe cylinder 38 thereof by jmeansof two springs 39 and 40 as shown, the band being also directly connected to but electrically insulated from an armature or contact finger 41. The springs 39 and 40 are so'proportioned that the contact linger 11 is biased toward the right to the position represented by-the-dotted line when no'potential is applied to theelectro-static brake, but is moved intoengagement with the two stationary contacts/l2 and 43 when'the brake is energized. .As clearly-shown, the contact finger 41 acts directly to control the energization of a train control device TC, closing a circuitto this device when the relay 36 is energized and a potential is applied to the electro-static brake, and opening the circuit to de-energize tedevice TC when the relay 36 is de-energized. The armature or contact-finger 41, the springs 39 and 10 and the brake band 37 -in thedevice of Fig. 2 are preferably designed to'have a low natural period of vibration-so that these parts will not'respond to each interruption in the potential'applied to the brake and will thus maintain the contacts 41-2 and 4:3 continuously dol favorable traflic conditions.

of the brake may be obtained by so tuning the armature 44 and the contact reed 45 of the relay 35 that they will not respond to each cycle of the control current, thereby maintaining the contact reed 45 in engagement with its stationary contact 46 so that the potential applied from the battery 47 to the electrostatic brake is continuous so long as alternating currents flow in the track rails.

It is evident that the operation of the system shown in Fig. 2 under the various traffie conditions is identical with that described above in connection with Figure 1, and for this reason no further detail description of its operation will be given.

In Figure 3, a second modification of the car-carried apparatus has been shown. In this embodiment a different application of the electrostatic brake principle is utilized. A block of agate or other semi-conducting material 50 is shaped with a plane surface 51 and a curved surface 52, these surfaces being opposite to each other. A contact plate 53' is secured in intimate contact with the plane surface 51, and a flexible contact strip of conducting material 54 is secured tangent "to and in intimate engagement with one end of the curved surface 52, the strip 54 having natural bias away from the curved surface 52 of the semi-conductor to a position represented by the dotted line; Stationary contacts 55 and 56 are provided for engagement by the extended free end of the strip 54 when in its attracted position as shown. Yi hen a difference of potential is impressed between the plate 53 and the strip 54, the adhesion between the strip 54 and the semi-conductor 50 causes the band to cling to the curved surface 52, thus moving the strip to the position shown and closing the contacts 55 and 56.

The application of the embodiment shown in Fig. 3 to the car-carried apparatus of a train control system is clearly evident from the drawing. A sensitive electro-mechanical relay 57 is provided, being energized by the impulses received from the trackway, and acts to apply a potential from the battery 58 to the plate 53 and the strip 54, causing the contacts 55 and 56 to be closed and the train control device TO to be energized un- When no train control currents flow in the track rails the relay 57 is de-ener 'ized and'the potential is cut off from the electrostatic device, thus permitting the strip 54 to assume its de-energizing position as shown by the dotted line, and ale-energizing the train control device TC. thus causing a restrictive control. The armature 59 and the contact reed 60 of the relay 57 used in the embodiment shown in Fig. 3 are suitably constructedto have a low natural period of vibration so that the potential from the battery 58 Will be constantly applied to the electrostatic device While the train control impulses are being received. I I

From the above description it is seen that a very simple and inexpensive amplifying means for use in connectionwith automatic train control systems has been devised. This amplifying means employs the electrostatic brake principle in which appreciable currents may be controlled by very slight variations in voltage, which condition is very desirable in a train control system.

,As the present invention has been described in a rather specific mannerand in connection with certain specific devices and circuits, it should be clearly understood that certain changes,-combinations and modifications may be madewithout departing from the scope of the invention as defined by the appended claims. i \Vhat itis desired to secure by Letters Patent" is 1. In an automatic train control system, means for inductively transmitting infiuences from the trackway to a moving vehicle, amplifying means comprising a relay normally energized by said transmitted infiuences, an electrostatic brake device controlled by said relay and means for controlling the progress of the vehicleby said electrostatic brake device.

2. In an automatic train control system, trackway means for transmitting influences to a movingvehicle, car-carried means for receiving said influences while the vehicle is in motion, means for amplifying said influences including an electrostatic device and train control means controlled by said electrostatic device.

3. In an automatic train control system, car-carried apparatus comprising a receiving circuit for inductivelyreceiving influences transmitted from the trackWay, a relay connected in said circuit and having a vibratory member, a stationary contact adapted to be engaged by said vibratory member when said influences are received, a source of potential controlled by said vi bratory member and said contact,'and an electrostatic device controlled by said controlled source of potential.

4. In an automatic train control system, car-carried apparatus comprising, a receiving circuit adapted to receive influences transmltted from the trackway, a relay in said circuit having a vibratory member, a

second circuit including said vibratory mem-' her, a contact and a source of potential in series, and an electrostatic device in said second circuit adapted to be operated by said source of potential and to be controlled by said vibratory member and said contact.

.5. In an automatic train control system, car-carried apparatus comprising a relay having a vibratory contact member, receiving means for operating said relay in accordance with. influe c J a smitt d from the trackvvay, a source of potential controlled by said vibratory contact member, and an electro-static device including a conducting element and .a semi-conducting element, adapted to be operated by said controlled source of potentialr I a 6. In ,an automatic trainvcontrol system, trackway means for transmitting influences to a moving vehicle, a car-carried control device for controlling the progress of the vehicle,and car-carried means for amplifying said influences comprising, a relay operated by said influences, a circuitincluding a source of potential controlled by said relay, two conducting members adjacent to and in engagement with a semi-conducting member, said conduct-ingmembers being connected to said controlled source of potential, and means for controlling the operation of said control device by one of said conducting members.

7 In an automatic train control system, a car-carried. receiving circuit, trackway means for energizing said circuit with currents of pre-determined frequency, and carcarried apparatus comprising, a relay energized by receiving circuit and having a vibratory contact system which is mechanically tuned to resonate at said pre-determined frequency, a source of potential controlled by said vibratory contact system, an electro-static relay including a conducting element and a semi-conducting element ac'lapted to be operated by said controlled source of potential, and train control means governed by said electro-static relay.

-8. In anamplifying system, a receiving circuit, a vibratory relay connected in said receiving circuit, a source of potential controlled by ,said vibratory relay, an electrostatic device operated by said controlled sourceof potential, and means for controlling a circuit by said electro-static device.

9. In an amplifying system, areceiving circuit, a relayenergized'by currents in said receiving circuit and having a vibratory contactsystem tuned to resonate at a pre-determined frequency, a, source of potential controlled by said vibratory contact system and an electrostatic device including a conductor and asemi-conductor governed by said controlled source of potential.

10. In an automatic train controlsy stem,

an inductive car-carried receiving circuit, trackway sane ans for inducing currents in said receiving circuit, car-carried apparatus including a relay energized by said receiving circuit, a mechanically tuned vibratory contact on said relay, an electro-static device comprising a semi-conducting element in intimate contact with two conducting elements, a source of potential controlled by said vibratory contact and applied to said nduc g element and means for ontrolling a train control device by one of said conducting elements.

11. In an automatic tra n control system,

an inductive car-carried receiving circuit electrically tuned to resonate at apredetermined frequency, trackway means for inducing currents of said frequency in said receiving circuitunder favorable traffic co'nf ditions only, car-carried apparatus includ ing arelay energized by said receiving circuit, said relay having a vibratory contact mechanism tuned to resonate at said predetermined frequency, an electrostatic device comprising a' semiconductor and I a plural} ity of conductors, a source of potential con trolled by said vibratory contacts and applied to said conductors, and a train control device controlled by one of said conductors.

12. In an automatic control system, an in ductive receiving circuit, trackway means for inducing currents in said receiving c'ir cuit, car-carried apparatus comprising a relay connected in series with saidrec'eiving' circuit, a contact controlled by said relay, an electrostatic device comprising a mova ble semi-conducting element in intimate contact with a plurality of conducting elements,

means for continuously moving said semi;

conducting element, a source of potential applied to :said conducting elements in accordance withthe' operation of said relay contact, andmeans for governing the opera; tion of a train control device in accordance with the motion of one of said conducting elements.

,13. In an automaticcontrol system, an inductive receiving circuit, trackway means for inducing currents in said receivingcin' cuit, car-carried apparatus comprising a relay connected in series with said receiving circuit, a vibratory contact controlled by said relay, an electrostatic translating device comprising a movable semi-conducting element, a movable conducting element rigidlyconnected to and .in intimate contact withasaid semi-conducting element and a second movable conducting element in inti- ,m ate contact with said semi co1iducting element, meansfor continuously moving said semi-conductingv element and said rigidly connectedconducting element, a source of electrical potential, means including said vi: bratory contact forapplying said source of potential ,between said conducting elements of said electrostatic devicefl whereby said second movable conducting element is moved by-said semi-conducting element, and means for controlling a traincontrol device in accordance with the motion of said second movable conducting element.

14. In an automatic control system, an inductive receiving circuit, trackway means for inducing currents in said receiving circuit, car-carried apparatus comprising a relay connected in series with said receiving circuit, a vibratory contact controlled, by said relay and tuned to resonate at a predetermined frequency, an electrostaticde vice comprising a semi-conductor rotatably mounted on a conducting shaft, means for continuously rotating said shaft and said semi-conductor, a movable conducting element in intimate contact with said. semiconductor, a source of electrical potential applied between said conducting shaft and said conducting element, said potential being controlled in accordance with the vibration of said vibratory element, whereby said 7 conducting element is moved by said semi mechanically tuned to resonate at said pre determined frequency, an'electro-static device comprising a semi-conducting element mounted on a conducting shaft, means for continuously rotating said shaft and said semi-conductor, aconducting element biased into intimate contact with said semi-conductor, means including a source of electrical potential and saidrvibratory contact for applying a difference of potential between said conducting shaft and said conducting element in accordance with said predetermined frequency,whereby said conducting element is moved at said predetermined frequency by said send-conducting clement, vehicle control means acting when energized to prevent a restrictive control and means whereby said control means is energized when said conducting element is moved at said predeterminedfrequency. i p

16. In an automatic train control system, traclrway means for transmitting influences to a moving vehicle,car-carried means for receiving said influences while the vehicle is in motion, means for amplifying said influences including a device responsive to e'lectro-static forces, and train control. means controlled by said device. I

I 17. In an automatic train. control system,

trackway means for'transmitting influences to a moving vehicle, car-carried means for receiving said influences While the vehicle 1s in motion, means for amplifying said in-- fluenccs including a mechanically driven device controlled in accordance with electrostatic influences impressed thereon, and train control means controlled by said'devioe.

'18. In an automatic train control system, car-carried apparatus comprising a receiving circuit for-inductively receiving influences transmitted from the trackway, a'relay connected in said circuit and having a vibratory member, a stationary contact adapted to be engaged by said vibratory member when said influences are received, asource of potential controlled by said vibratory member and said contact, and a driven electro-static device'controlled by said controlled source of tiotential.

19. In an automatic train control system, carrarricd apparatus comprising areceivin circuit for inductively receiving influences transmitted from the trackway, a: relay connected in said circuit and'having a' vibratory member, a stationarycont'act adapted to be engaged by said vibratory member when said influences are received, a source'of pojtential controlled by said vibratory member and said contact, and a device responsive to, and having means for impressing thereon, electrostatic forces,.controlled by said controlled source of potential.

'20. In an automatic'train control system, car-carried apparatuscomprising, a receiving circuit adapted to receive influences transmitted from the trackway, a relay in said circuit having a'vibratory member, a

second circuit including said vibratory mem ber, a contact and a source of potential in series, and a device, controlled by static electrical forces, insaid second circuit adapted to be operated by said source of potential and to be controlled by said vibratory member and said contact.

21. In an amplifying system, a receiving circuit, a vibratory relay connected in said receiving circuit, a source of potential controlled by said vibratory relay, a device responsive to electro-static forces, operated by said controlled source of potential, and means for controlling a circuit by said electro-static device.

In testimony whereof I aflix my signature.

EDWARD H. LoFT'IN. 

